Er, weren't the Microsoft wheels for Xbox 360 doing this? I distinctly remember the Wireless Racing Wheel as well as the Fanatec CSR having additional vibration motors for extra effects. If I recall the general consensus was that it was a better and more realistic driving experience to just switch them off.
Are we really bragging about something that Microsoft discovered wasn't a great idea ten years ago?
Canned effects are ones that aren't based on any physical phenomena. Generally, FFB should emulate what you would feel in a real car through the steering wheel. Therefore, only effects that put force into the steering column would be felt.
However, because when you're playing a game you don't have the standard "butt sensor", many games find it preferable to add in things like vibration and such to the steering wheel. If you drive over a rumble strip in a real car there's no real effect on the steering, but in games they'll often vibrate the steering so that you have at least some sort of indication. Similarly there are often changes to the effects of over and understeer from what would be purely realistic.
Think of sound effects in movies. They're not real, they're added to enhance the realism. The same idea is in play here, there are additional FFB effects that are added to "enhance" the FFB. However, if you're a serious driver they can actually be quite detrimental to your ability to drive well, as the tactile information you're receiving is not the same as what you've spent likely thousands of hours practising.
I'll let Inside Sim Racing clarify how the T-GT works and how good/bad it is: